A movement mechanism of a conventional engine is a crank and connecting rod mechanism. Reciprocating movement of the piston is required to be transferred to the crankshaft through the link rods connected thereto. During the motion thereof, the link rods swing to and fro with the motion of the piston so as to keep the piston to undergo a periodical lateral force varied in a high step function.
Due to the presence of link rods in the crank and connecting rod mechanism, the crank and connecting rod mechanism internal combustion engines are bulky, heavy, and of poor balance performance. To address these problems, a Chinese patent document CN85100358B discloses a “crank-circular slider reciprocating piston type internal combustion engine”, characterized in that it omits the link rods and adopts the cooperation between a circular slider with an eccentric hole and specifically designed piston assembly so as to realize the conversion of the linear reciprocating motion of the piston into the rotary motion.
Based on the above mentioned patent documents, the Chinese patent document CN1067741C discloses a “crank double slider reciprocating piston type internal combustion engine” which is realized in the form of pairing of the piston and the dynamic balance slider, which respectively move along the tracks vertical to each other. The piston and the dynamic balance slider overcome the motion point each other so as to avoid the negative influence on life span of the mechanism when utilizing the gear mechanism to overcome the motion point; meanwhile the resultant force due to movements of the piston and the dynamic balance slider forms a centrifugal force directed to the center of the crank pin from the centre of the crankshaft so as to facilitate the balance in order to obtain an ideal effect of dynamic balance. The problems in the mechanism lie in that the distance L between the piston and the dynamic balance slider along the axis of the crankshaft exists so that they form a bent moment on the crankshaft so that the whole mechanism cannot balance completely.
Chinese patent document CN1144880A discloses a “crank-multi-circular slider reciprocating piston type internal combustion engine” in which the motion mechanism utilizes three-circular-slider mechanism comprising a reciprocating motion group formed of three reciprocating parts in which the reciprocating tracks of the two reciprocating motion parts on both end sides are parallel to each other; the reciprocating motion track of the middle reciprocating motion pan sandwiched between the reciprocating motion parts is vertical to the said two reciprocating motion tracks of the said two reciprocating parts on end sides; the mass of the middle reciprocating motion part is the sum of the masses of the two reciprocating parts on end sides and the mass of the circular slider mounted in the middle reciprocating motion part is the sum of the masses of the circular sliders mounted in the reciprocating motion parts on end sides. The three circular sliders are secured to each other to form a circular slider group in which the circular sliders on end sides are mounted on the same phase; the middle circular slider is mounted offsetting a 180 degree phase difference compared to the circular sliders on end sides. The eccentric hole of the above mentioned three circular sliders fits over a same one crank pin.
In the above mentioned three-circular-slider mechanism, all the reciprocating inertial force finally are combined into a rotary inertial force so as to facilitate the realization of balance by provision of a balance element. And the size of the middle reciprocating motion part is set to be just located in the middle of the two reciprocating parts on end sides so that the whole mechanism will not form a bent moment on the crankshaft, that is to say, in theory, the mechanism can accomplish a complete balance effect. However the better balance effect so relies on the middle reciprocating motion part, which makes the whole mechanism too complicated. Moreover, due to increased number of the reciprocating motion parts, the length of the crank pin is required to be increased causing the rigidity of the axis system reduced. In addition, the manufacturing cost of the machine is increased notably; the reliability can be reduced. The machine requiring a small size will not possibly utilize the above mentioned mechanism.
The crank circular slider mechanism provided in the above mentioned documents can realize interchange between reciprocating motion and rotary motion and therefore not only become a motion mechanism of the internal combustion engine for conversion from reciprocating motion to rotary motion, but be used in a compressor or a vacuumizer for conversion from rotary motion to reciprocating motion.